Adaptive power capping in a chip

ABSTRACT

Adaptive power capping in a chip that includes a plurality of cores in a processing system is provided. An active power demand for the chip is dynamically determined based on observed events of the cores. An average temperature of the chip is computed using one or more on-chip thermal sensors in the cores to estimate leakage power of the chip. A power capping threshold that incorporates the estimate of leakage power is determined based on the average temperature of the chip. Power capping is performed by throttling the cores based on determining that the active power demand for the chip exceeds the power capping threshold.

BACKGROUND

The present application relates generally to computer system performanceadaption. More specifically, the present application is directed toadaptive power capping in a chip of a processing system.

High performance and high reliability computer systems typically requireredundancy. However, redundant power system components are expensive,and there is a trade-off between initial system cost and operation underloss of redundancy. When redundancy is lost for power supply components,power (or electric current) must be limited to protect against exceedingcomponent specifications to avoid adverse results. In some systems, aloss of redundancy in power distribution can cause a sudden power-downor chip failure if the current demand exceeds power component limits.Reducing system performance by lowering clock frequency and voltage isone option to avoid exceeding component specifications by assuming worstcase conditions; however, system performance may be reduced for asubstantial period of time until system maintenance/repair is performed.

SUMMARY

A method is provided for adaptive power capping in a chip that includesa plurality of cores in a processing system. An active power demand forthe chip is dynamically determined based on observed events of thecores. An average temperature of the chip is computed using one or moreon-chip thermal sensors in the cores to estimate leakage power of thechip. A power capping threshold that incorporates the estimate ofleakage power is determined based on the average temperature of thechip. Power capping is performed by throttling the cores based ondetermining that the active power demand for the chip exceeds the powercapping threshold.

Embodiments also include a processing system that includes a redundantpower system and a processor chip that includes a plurality of cores.The processor chip is operable to dynamically determine an active powerdemand for the processor chip based on observed events of the cores. Anaverage temperature of the processor chip is computed using one or moreon-chip thermal sensors in the cores to estimate leakage power of theprocessor chip. A power capping threshold that incorporates the estimateof leakage power is determined based on the average temperature of theprocessor chip. Power capping is performed by throttling the cores basedon detecting a redundancy state of the redundant power system anddetermining that the active power demand for the processor chip exceedsthe power capping threshold.

Embodiments also include a computer program product. The computerprogram product includes a computer readable storage medium havingcomputer readable program code embodied therewith. The programinstructions are executable by a processor chip to cause the processorchip to dynamically determine an active power demand for the processorchip based on observed events of the cores. An average temperature ofthe processor chip is computed using one or more on-chip thermal sensorsin the cores to estimate leakage power of the processor chip. A powercapping threshold that incorporates the estimate of leakage power isdetermined based on the average temperature of the processor chip. Powercapping is performed by throttling the cores based on determining thatthe active power demand for the processor chip exceeds the power cappingthreshold.

Additional features and advantages are realized through the techniquesof the present invention. Other embodiments and aspects of the inventionare described in detail herein and are considered a part of the claimedinvention. For a better understanding of the invention with theadvantages and the features, refer to the description and to thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The forgoing and other features, and advantages ofthe invention are apparent from the following detailed description takenin conjunction with the accompanying drawings in which:

FIG. 1 is an overview flow diagram in accordance with an embodiment;

FIG. 2 is an exemplary diagram of a processing system in accordance withan embodiment;

FIG. 3 illustrates a flow diagram of a process for adaptive powercapping in accordance with an exemplary embodiment;

FIG. 4 is an exemplary diagram of a processing system in accordance withan embodiment;

FIG. 5 illustrates a flow diagram of a method for setting a powercapping threshold in accordance with an exemplary embodiment;

FIG. 6 illustrates a flow diagram of a method for power-proxy circuitoperation in accordance with an exemplary embodiment;

FIG. 7 depicts an exemplary diagram of a portion of a processor chip inaccordance with an embodiment; and

FIG. 8 illustrates a flow diagram of a process for adaptive powercapping in accordance with exemplary embodiments.

DETAILED DESCRIPTION

Exemplary embodiments perform adaptive power capping and powerthrottling in a chip. Embodiments can approximate active power demanddynamically using processor core events that define core activity.On-chip thermal sensors in processor cores can be used to calculate anaverage temperature of the chip to estimate leakage power. Embodimentsinclude an on-chip microcontroller to compute a total chip-power proxy.A lookup table may be used to determine the chip power capping thresholdfor the current chip-average temperature and throttle/un-throttle thechip (i.e., reduce/resume activity in all cores simultaneously) if thechip-power proxy exceeds or is below the power capping threshold.Alternate embodiments use the on-chip microcontroller to determine thechip power capping threshold for the current chip-average temperatureand write the threshold value to a chip-level hardware register. On-chiplogic circuits can compute a total active power demand for all of thecores, compare the total active power demand with the threshold in thechip-level hardware register, and throttle/un-throttle processing on thecores.

The exemplary embodiments may be implemented for a variety of processorsof various computing devices. For example, exemplary embodiments may beused for any of a server computing device, client computing device,communication device, portable computing device, or the like. FIGS. 2and 4 are provided hereafter as examples of a processing system in whichexemplary aspects of the illustrative embodiments may be implemented.FIGS. 2 and 4 are only exemplary and are not intended to state or implyany limitation with regard to the types of computing devices in whichthe illustrative embodiments may be implemented.

FIG. 1 depicts an overview process flow 10 according to embodiments. Atblock 12, a service engine that is an embedded microcontroller on a chipperforms many functions, one of which is reading and communicatingsensor data. Chip sensors can include temperature, power proxy, andvoltage data. At block 14, sensor data is collected, except for thepower proxy. The service engine can also read a chip product data memorydevice (CPROM) at block 16 to collect chip leakage data from chip vitalproduct data (VPD) leakage records. At block 18, temperature data fromthe sensors and optionally the leakage data from the CPROM can be usedto estimate static power via a lookup table. At block 20, the powerproxy data is collected and summed to estimate dynamic power from allcores of the chip. A power subsystem redundancy state is read at block22. Depending whether zero or more power elements fail, the total powerlimit changes. At block 24, a total power estimate from the static anddynamic power proxies is compared with the power limit based on aredundancy state. If the estimated total power is above the limit, athrottle command is sent to all cores of the chip at block 26, whichlowers the power by interrupting the instruction execution flow, forinstance, by the insertion of idle or “no-op” cycles. If the total powerdrops below the limit, throttling is removed at block 28. The processflow 10 then returns to block 14 to perform as a continuous monitor.

Turning now to FIG. 2, a processing system 100 is generally shown thatincludes a processor chip 102 (also referred to as chip 102) thatincludes a service engine 104 implemented in an on-chip microcontroller.A timer 106 can be used to establish synchronization and control timingof sensor data acquisition and control operations. The processor chip102 also includes a plurality of cores 108. The cores 108 can includecircuitry such as functional units to fetch, decode, execute, andcomplete instruction streams. The cores 108 of FIG. 2 also each includea hardware power-proxy circuit 110 and at least one on-chip thermalsensor 112. Other sensors and logic circuits (not depicted) can also beincluded in the cores 108.

The processing system 100 includes a redundant power system 114 thatincludes one or more redundant power sub-systems. For example, theredundant power system 114 can include redundancy for point-of-loadpower components and/or for distributed converter assembly components.The redundant power system 114 may supply alternating current (AC)and/or direct current (DC) power to components of the processing system100. A redundancy state 116 of the redundant power system 114 may bedetected by the service engine 104 or a redundancy state 116 can be sentto the service engine 104 by a system health monitor (not depicted). Theredundancy state of the power system may have multiple levels dependingon what power components failed. Loss of one or two point of loadelements will indicate different redundancy states, as will loss of adistributed converter assembly. In general, there will be differentpower capping limits depending on the redundancy state.

The service engine can also communicate to the CPROM 115 containing theVPD which contains the chip leakage current or power at knownconditions. This can be used to calculate the chip leakage power asdescribed later. The service engine 104 can communicate with the cores108 via bus 118. The cores 108 can send power and temperature data 120to the service engine 104 via bus 118. The service engine 104 can sendthrottle commands 122 (including un-throttle commands) to the cores 108on bus 118. In an embodiment, the service engine 104 collects thepower-proxy and thermal sensor values from the power-proxy circuit 110and on-chip thermal sensor 112 from every core 108 periodically as powerand temperature data 120 using the timer 106.

The service engine 104 can compute a chip-level power-proxy sum (i.e., atotal active power demand), an average temperature of the chip 102, anda power capping threshold for the average temperature using a lookuptable 125. The service engine 104 can compare the power-proxy sum to thepower capping threshold. If the threshold is exceeded, throttling can beissued to all cores 108. Throttling may include insertion of idle cyclesto reduce power consumption. If the threshold is not exceeded,throttling can be removed from all cores 108.

In an embodiment, each power-proxy circuit 110 is configured to sampleand store values at a regular interval (e.g., every 3.2 milliseconds).The service engine 104 can read all the sensors (e.g., on-chip thermalsensors 112) on chip 102 periodically in a loop (e.g., every 16milliseconds). If the power-proxy circuits 110 are sampled morefrequently than the on-chip thermal sensors 112, the power-proxycircuits 110 can be read multiple times per loop. The service engine 104may be configured to read all sensors (e.g., on-chip thermal sensors112) at the start of a loop, and after that read the power-proxycircuits 110 multiple times within a loop. To ensure that thepower-proxy sample is stable, when the service engine 104 is reading thevalue, a time offset can be added.

FIG. 3 illustrates a flow diagram of a process 200 for adaptive powercapping in accordance with an exemplary embodiment and is described withrespect to FIG. 2. At block 202, the service engine 104 and thepower-proxy circuit 110 of each core 108 are started. At block 204, theservice engine 104 waits for half of the power proxy sampling time. Atblock 206, sensors, such as on-chip thermal sensors 112, of chip 102 areprocessed except for the power-proxy circuits 110. At block 208, a waitcan be performed for the power proxy sample time plus an offset toensure stable sample values. At block 210, power proxy values can beread from the power-proxy circuit 110 of each core 108 and summed as atotal active power demand. At block 212, a check for a redundancy state116 is performed. If there is a redundancy state 116 indicatingredundancy loss, then at block 214 a power capping threshold isdetermined by looking up the average temperature in the lookup table125. At block 216, the power-proxy sum (total active power demand) iscompared to the power capping threshold. The service engine 104 may sendthrottle commands 122 to the cores 108 at block 218 based on determiningthat the power-proxy sum (i.e., total active power demand) is greaterthan or equal to the power capping threshold. Otherwise, at block 220,throttling is cleared (i.e., un-throttle).

After a throttling determination has been made at block 216 or if theredundancy state 116 detected at block 212 indicates no redundancy loss,then at block 222 waiting is performed for the power proxy sample time.At block 224, a check is performed to determine whether N (e.g., 5)proxy samples have been taken. If not, then the flow returns to block210. If N proxy samples have been taken, then at block 226, a check isperformed to determine whether it is time to return to block 206 andprocess chip sensors again (e.g., time >=N multiplied by the proxysample time).

FIG. 4 is an exemplary diagram of a processing system 300 in accordancewith an embodiment. Similar to the processing system 100 of FIG. 2, theprocessing system 300 of FIG. 4 includes a processor chip 302 (alsoreferred to as chip 302) that includes a service engine 304 implementedin an on-chip microcontroller. A timer 306 can be used to establishsynchronization and control timing of sensor data acquisition andcontrol operations. The processor chip 302 also includes a plurality ofcores 308. The cores 308 can include circuitry such as functional unitsto fetch, decode, execute, and complete instruction streams. The cores308 of FIG. 4 also each include a hardware power-proxy circuit 310 andat least one on-chip thermal sensor 312. Other sensors and logiccircuits (not depicted) can also be included in the cores 308. Similarto processing system 100 of FIG. 2, a redundancy state 316 of aredundant power system 314 may be detected by the service engine 304 ora redundancy state 316 can be sent to the service engine 304 by a systemhealth monitor (not depicted).

The service engine can also communicate to the CPROM 315 containing thechip vital product data which contains the chip leakage current or powerat known conditions. This can be used to calculate the chip leakagepower as described later. The service engine 304 can communicate withthe cores 308 via bus 318. The cores 308 interface with timer 306 viasynchronization bus 320. The cores 308 can also interface with a chippower proxy 324 via power/throttle bus 322. Although the bus 318,synchronization bus 320, and power/throttle bus 322 are depicted asseparate buses, one or more of the buses 318-322 can be combined orfurther partitioned in embodiments. Various commands and data can betransmitted over the buses 318-322. For example, bus 318 may be used bythe service engine 304 to read temperature data 326 from on-chip thermalsensors 312 of cores 308. The power/throttle bus 322 can be used to sendpower proxy data from power-proxy circuits 310 of cores 308 to chippower proxy 324 and for chip power proxy 324 to sendthrottle/un-throttle commands to cores 308. In the example of FIG. 4,the chip power proxy 324 is implemented in hardware for faster responsetime and to reduce processing burdens on the service engine 304.

FIG. 5 illustrates a flow diagram of a method 400 for setting a powercapping threshold in accordance with an exemplary embodiment and isdescribe with reference to FIG. 4. In method 400, at block 402, theservice engine 304 and the power-proxy circuit 310 of each core 308 arestarted. At block 404, sensors, such as on-chip thermal sensors 312, ofchip 302 are processed except for the power-proxy circuits 310. At block406, a redundancy state check 316 is performed. If the redundancy state316 indicates a loss of redundancy then at block 408 a power cappingthreshold is determined by looking up the average temperature in thelookup table 325. At block 410, the power capping threshold is writtento a chip-level register (e.g., a chip power-proxy threshold register)of the chip power proxy 324. There may exist a different power cap limitfor each redundancy state. After block 410 or if there was no redundancystate 316 detected at block 406, then at block 412, a check is performedto determine whether it is time to return to block 404 and process chipsensors again (e.g., time >=16 milliseconds).

The method 400 can be performed by service engine 304 of FIG. 4 whilemethod 500 of FIG. 6 is performed by the chip power proxy 324 of FIG. 4.In method 500, at block 502, the power-proxy circuit 310 in each of thecores 308 sample core activity in a synchronous manner (e.g., usingtimer 306) and transfer data to the chip power-proxy 324. At block 504,a circuit of the chip power proxy 324 adds all individual corepower-proxies, compares them with the chip power-proxy thresholdregister and throttle/un-throttles processing on all cores 308.

Interactions between the chip power proxy 324 and cores 308 are furtherdepicted in FIG. 7. Various functional units 602 (e.g., execution units,load/store units, floating-point units, fixed-point units, instructionfetching units, completion units, etc.) of each core 308 can providecore events 604 to a power-proxy circuit 310 which provides localizedpower proxy data to a summing circuit 606 of the chip power proxy 324 toproduce a total active power demand. A threshold checker 608 can comparethe total active power demand with a power capping threshold stored in athreshold register of the chip power proxy 324 to determine whether tocommand a throttle actuator 610 in each core 308 to throttle/un-throttleprocessing.

Power-proxy estimation in hardware (e.g., by power-proxy circuit 110 ofFIG. 2 or power-proxy circuit 310 of FIGS. 4 and 7) can be performed bydefining core events that represent activity, such as a number ofinstructions executed per second and/or activity of particularfunctional units 602 of the cores 308. Weights for core events 604 canbe obtained through a calibration process. A power-proxy value can beestimated as dynamic AC power according to equation 1.

Power-proxy value=A*SUM(Wi,Ci)+K  (Equation 1)

Equation 1 can be a linear fit in the form y=mx+x, where A=m and K=c. Wis a weight for a core event “i”. C is a count value of core event “i”.A is a calibration scaling factor. K is a calibration constant.

A power capping table (e.g., lookup table 125, 325) may be generated bytaking leakage current into account. A current-cap value can be selectedand the corresponding power can be adjusted for the system load-line ata nominal voltage for the worst-case chip. Leakage current can becomputed at an idle state of the chip (i.e., no workload running).Leakage current for temperature can be computed using equation 2.

Ivdd_leak_corrected=Ivdd_leak*1.25̂((T_run−T_idle)/10)Amps  (Equation 2)

In equation 2, T_idle is a constant. DC power can be computed usingequation 3.

Vdd_power_DC_v1=Ivdd_leak_corrected*Vdd Watts  (Equation 3)

An AC power-cap can be computed using equation 4.

power_set_point−Vdd_power_DC_v1  (Equation 4)

The AC power-cap can be converted to a corresponding power-proxy valueas described by equation 1. Equations 2-4 can be computed for a widerange of temperatures to generate a power capping table stored in memoryof the service engine 104, 304. Another approach is to use the chip VPDrecord containing the leakage power and current at known voltage andtemperature. This data is collected at chip test conditions along withother chip VPD data including intrinsic chip speed (as given by on chipring oscillators for example), or chip nominal voltage. The estimatedleakage or DC current can be calculated at any voltage V1 andtemperature T1 from the leakage current Ivdd_leak0 in the VPD recordthat was determined at voltage V0 and temperature T0 from the followingequation. Vdoub is the doubling voltage (the change in voltage in Voltsthat doubles the leakage current) and is 0.15V in the presentembodiment. Tdoub is the analogous doubling temperature in degreesCelsius and is 30 C in the present embodiment. This equation is specificto this implementation but is generally semiconductor technologydependent and can be determined for each technology by one skilled inthe art.

Ivdd_leak1(V1,T1)=Ivdd_leak0(V0,T0)*2̂((V1−V0)/Vdoub)*2̂((T1−T0)/Tdoub)

Leakage power Vdd_power_DC_v1=Ivdd_leak(V1,T1)*V1

V1 and T1 are in Volts and degrees Celsius respectively and may bedetermined from sensor readings. FIG. 8 illustrates a flow diagram of amethod 700 for adaptive power capping in accordance with an exemplaryembodiment. FIG. 8 is described in reference to FIGS. 1-7 and may beperformed in an alternate order and include additional steps beyondthose depicted in FIG. 8. In some embodiments, an on-chipmicro-controller (e.g., service engine 104, 304) computes a total activepower demand and controls the throttling of the cores. In alternateembodiments, an on-chip micro-controller (e.g., service engine 104, 304)determines the power capping threshold and writes the power cappingthreshold to a chip-level register, and the on-chip logic circuitscompute a total active power demand from the cores 108, 308 and controlthe throttling of the cores 108, 308.

At block 705, an active power demand for a processor chip 102, 302 isdynamically determined based on observed events of the cores 108, 308.Active power demand may be computed by service engine 104 or chip powerproxy 324 in embodiments.

At block 710, an average temperature of the processor chip 102, 302 iscomputed by service engine 104, 304 using one or more on-chip thermalsensors 112, 312 in the cores 108, 308 to estimate leakage power of theprocessor chip 102, 302. The active power demand can be determined at ahigher frequency than the average temperature is computed.

At block 715, a power capping threshold that incorporates the estimateof leakage power is determined by service engine 104, 304 based on theaverage temperature of the processor chip 102, 302. The power cappingthreshold can be determined using the average temperature of theprocessor chip 102, 302 to index into a power capping table (e.g.,lookup table 125, 325) comprising a plurality of power cappingthresholds that are predetermined based on a leakage power model of areference chip.

At block 720, the cores 108, 308 are throttled to perform power cappingbased on determining that the active power demand for the processor chip102, 302 exceeds the power capping threshold. The throttling of thecores 108, 308 can be based on detecting a redundancy state 116, 316 ofa redundant power system 114, 314 of the processing system 100, 300.Throttling the cores 108, 308 can be performed by selectively insertingidle cycles at each of the cores 108, 308 to decrease processingthroughput by lowering usage of functional units 602 of the cores 108,308. The cores 108, 308 can also be un-throttled to remove thethrottling based determining that the active power demand for theprocessor chip 102, 302 does not exceed the power capping threshold.Un-throttling can stop inserting additional idle cycles to increaseprocessing throughput, for example.

It should be noted that the flowchart and block diagrams in the figuresillustrate the architecture, functionality, and operation of possibleimplementations of systems, apparatuses, methods and computer programproducts according to various embodiments of the invention. In thisregard, each block in the flowchart or block diagrams may represent amodule, segment, or portion of code, which comprises at least oneexecutable instruction for implementing the specified logicalfunction(s). It should also be noted that, in some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts, or combinations of special purpose hardware andcomputer instructions.

The present invention may be a system, a method, and/or a computerprogram product. The computer program product may include a computerreadable storage medium (or media) having computer readable programinstructions thereon for causing a processor to carry out aspects of thepresent invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Smalltalk, C++ or the like, andconventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

This disclosure has been presented for purposes of illustration anddescription but is not intended to be exhaustive or limiting. Manymodifications and variations will be apparent to those of ordinary skillin the art. The embodiments were chosen and described in order toexplain principles and practical application, and to enable others ofordinary skill in the art to understand the disclosure.

Although illustrative embodiments of the invention have been describedherein with reference to the accompanying drawings, it is to beunderstood that the embodiments of the invention are not limited tothose precise embodiments, and that various other changes andmodifications may be affected therein by one skilled in the art withoutdeparting from the scope or spirit of the disclosure.

What is claimed is:
 1. A method of adaptive power capping in a chipcomprising a plurality of cores in a processing system, the methodcomprising: dynamically determining an active power demand for the chipbased on observed events of the cores; computing an average temperatureof the chip using one or more on-chip thermal sensors in the cores toestimate leakage power of the chip; determining a power cappingthreshold that incorporates the estimate of leakage power based on theaverage temperature of the chip; and throttling the cores to performpower capping based on determining that the active power demand for thechip exceeds the power capping threshold.
 2. The method of claim 1,wherein the power capping threshold is further based on vital productdata of the chip that includes leakage current at known temperature andvoltage, and the method further comprising: un-throttling the cores toremove the throttling based determining that the active power demand forthe chip does not exceed the power capping threshold.
 3. The method ofclaim 1, wherein the throttling of the cores is further based ondetecting a redundancy state of a redundant power system of theprocessing system.
 4. The method of claim 1, wherein determining thepower capping threshold further comprises: using the average temperatureof the chip to index into a power capping table comprising a pluralityof power capping thresholds that are predetermined based on a leakagepower model of a reference chip.
 5. The method of claim 1, wherein theactive power demand for the chip is determined at a higher frequencythan the average temperature of the chip is computed.
 6. The method ofclaim 1, wherein an on-chip micro-controller computes a total activepower demand and controls the throttling of the cores.
 7. The method ofclaim 1, wherein an on-chip micro-controller determines the powercapping threshold and writes the power capping threshold to a chip-levelregister, and the on-chip logic circuits compute a total active powerdemand from the cores and control the throttling of the cores.
 8. Themethod of claim 1, wherein throttling the cores comprises selectivelyinserting idle cycles at each of the cores.
 9. A processing systemcomprising: a redundant power system; and a processor chip comprising aplurality of cores, the processor chip operable to perform a methodcomprising: dynamically determining an active power demand for theprocessor chip based on observed events of the cores; computing anaverage temperature of the processor chip using one or more on-chipthermal sensors in the cores to estimate leakage power of the processorchip; determining a power capping threshold that incorporates theestimate of leakage power based on the average temperature of theprocessor chip; and throttling the cores to perform power capping basedon detecting a redundancy state of the redundant power system anddetermining that the active power demand for the processor chip exceedsthe power capping threshold.
 10. The processing system of claim 9,wherein the power capping threshold is further based on vital productdata of the chip that includes leakage current at known temperature andvoltage, and the cores are un-throttled to remove the throttling baseddetermining that the active power demand for the processor chip does notexceed the power capping threshold.
 11. The processing system of claim9, wherein determining the power capping threshold further comprises:using the average temperature of the processor chip to index into apower capping table comprising a plurality of power capping thresholdsthat are predetermined based on a leakage power model of a referencechip.
 12. The processing system of claim 9, wherein the active powerdemand for the processor chip is determined at a higher frequency thanthe average temperature of the processor chip is computed.
 13. Theprocessing system of claim 9, wherein an on-chip micro-controllercomputes a total active power demand and controls the throttling of thecores.
 14. The processing system of claim 9, wherein an on-chipmicro-controller determines the power capping threshold and writes thepower capping threshold to a chip-level register, and the on-chip logiccircuits compute a total active power demand from the cores and controlthe throttling of the cores.
 15. The processing system of claim 9,wherein throttling the cores comprises selectively inserting idle cyclesat each of the cores.
 16. A computer program product comprising acomputer readable storage medium having program instructions embodiedtherewith, the program instructions executable by a processor chip tocause the processor chip to: dynamically determine an active powerdemand for the processor chip based on observed events of the cores;compute an average temperature of the processor chip using one or moreon-chip thermal sensors in the cores to estimate leakage power of theprocessor chip; determine a power capping threshold that incorporatesthe estimate of leakage power based on the average temperature of theprocessor chip; and throttle the cores to perform power capping based ondetermining that the active power demand for the processor chip exceedsthe power capping threshold.
 17. The computer program product of claim16, wherein the cores are un-throttled to remove the throttling baseddetermining that the active power demand for the processor chip does notexceed the power capping threshold.
 18. The computer program product ofclaim 16, wherein the throttling of the cores is further based ondetecting a redundancy state of a redundant power system of theprocessing system and wherein determining the power capping thresholdfurther comprises using the average temperature of the processor chip toindex into a power capping table comprising a plurality of power cappingthresholds that are predetermined based on a leakage power model of areference chip.
 19. The computer program product of claim 16, wherein anon-chip micro-controller computes a total active power demand andcontrols the throttling of the cores.
 20. The computer program productof claim 16, wherein an on-chip micro-controller determines the powercapping threshold and writes the power capping threshold to a chip-levelregister, and the on-chip logic circuits compute a total active powerdemand from the cores and control the throttling of the cores.